Fire extinguishing foam tube and spray head



Aug. 16, 1949- F. L. BOYD EI'AL FIRE EXTINGUISHING FOAM TUBE AND SPRAY HEAD Filed Oct. 25, 1944 f H 0M N Maw J Rw Es wm IE 5 Patented Aug. 16, 1949 FIRE EXTINGUISHING FOAM TUBE AN SPRAY HEAD Fisher L. Boyd. West Chester, and Lewis w.

Boer-ner, Newton Square,

Pa... assignors to National Foam System, Inc., Philadelphia, h, a corporation of Delaware Application October 25, 1944, Serial No. 500,260

2 Claims.

This invention relates generally to apparatus for producing foam for extinguishing fire and more particularly to improvements in the design and construction of the tub from which the foam is discharged in the form of a stream of considerable length.

In the production of the so-called air or mechanical foam for fire-extinguishing purposes, in order to obtain an adequate volume of foam in relation to the water used, it has been found necessary to finely subdivide and disperse the stream of water at the locus of'introduction of the air, not only to provide for a substantial increase in the total surface area of .the water, but also to provide for an intimate mingling of the water, the foam stabilizer or foam-forming material and the air in the mixing zone. The production of such foam is described more particularly in United States Letters Patent No. 2,106,043, granted January 18, 1938, and No. 2,198,585, granted April 23, 1940. 1

In the development of the art of producing mechanical foam, a great deal of attention has been devoted to the design and construction of new and improved means for mechanically subdividing or breaking up the flowing stream at the point or in the zone where air is to be eninto and through the conventional construction of foam discharge tube, such turbulence is created in the stream that upon its discharge from the exit end of the tube considerable weep- Having in mind the foregoing, it is among the objects of the present invention to provide a foam discharge tube of such improved design and construction as to insure the delivery therego through and discharge therefrom of a streamlined or laminar flow of foam as distinguished from a turbulent flow thereof, the resultant foam stream which issues from the tube being of relatively smooth external surface and of such compact form that substantially no weeping of the trained therein. While the creation of maximum turbulence in the flowing streamat the point or zone of entrainment therewith of the air is, of course, necessary in order to obtain the greatest amount of surface area of the water stream, the very existence of such turbulence in the foam stream has mllitated against its-discharg from the foam tube in a form and manner most effective for its intended purpose.

As is now well known in the art, mechanical foam is generally produced by delivering water to a discharger head or butt by means of which the water is finely sub-divided and co-mingled with a foam-forming liquid immediately prior to entrainment of air therewith, the sub-divided stream with the air entrained therein being directed into and through a tube for discharge in the form of a foam stream. Or, the water previously charged with the foam-forming liquid may be delivered to the discharger head or butt for subdivision and entrainment of air just prior to its delivery into and through the foam discharge tube. Both of these procedures are described as the pending application of Francis J. Hogenmiller, Serial No. 478,877, filed March 12, 1943.

In any case where the foam stream is so mestream occurs throughout its projected length.

More specifically, it is an object of the present invention to provide a foam discharge tube which is of such internal design and construction as to provide for such temporary reduction of the velocity of the foam stream as to convert its flow from a turbulent character to a streamlined character, while maintaining substantially constant the volume of the flow through the tube,

the arrangement and operation of the tube being such that upon issuance of th foam stream therefrom it retains its streamlined characteristics.

Other objects and advantages of the present invention will appear more fully hereinafter, it

being understood that the present invention consists substantially in the combination, construction, location and relative arrangement of parts, all as will presently appear, asshown in the ac-' companying drawings and as finally pointed out in the appended claims.

In the accompanying drawings, which are illustrative of a preferred embodiment of the present invention:

5o Figure 1 is an elevational view, partially in section. of the foam discharge tube of the present invention, the same being shown in operative association with the foam producing apparatus;;

Figure 2 is' an elevational view, partially in chanically sub-divided prior to its being directed section, of the stream discharge heador butt;

3 V Figure 3 isa transverse sectional view taken on the line 3-3 of Figure 1; and V Figure 4 is a transverse sectional taken 4 the turbulent stream enters the interior of the tube' 24, it entrains air therewith from atmos- Zphere with the result that a turbulent body of air foam is formed immediately beyond the'entrance end 25 of the foam discharge tube 28 for passage therethrough toward the open discharge end 26 of said tube, the foam being finally delivered fromsaid discharge end of the tube in the form of a stream capable of being projected to a suitable substance known in the art generally as stabilizers or foam-formers." If desired, the foam promoting agent may be preliminarily introduced into the water stream for delivery to the foam producer I8 in the form of a pro-mixed solution, or the foam promoting agent may be introduced into the water stream through the use of a stabilizer pick-up tube l2 which is so connected to the foam producer I8 that as the water stream passes therethroughit induces a suction which acts to draw the stabilizer into the water stream for conjoint discharge therewith from the discharge end of the device I8.

To this end, the device I8 is internally provided with a tubular member I3 having a central bore I 4 extending axially of the'device I8 and having a forward portion I5 of such reduced external diameter as to provide an annular chamber I6 between such portion and the surrounding inner wall of the main body I! of the device I8.-

The said main body I1 is fitted in its discharge end with a central discharge sleeve I8, the rear point considerably distant from its point of discharge from the tube. It is to control the physical characteristics of this foam stream that is the principal objective of the present invention.

The foam discharge tube as constructed in accordance with the principles of the present increased uniform diameter, the cross-sectional area of the intermediate section being thus materially greater than the cross-sectional areas of each of the opposite end sections of the tube. Further, it will be noted that the several sections are so relatively formed and joined together that the relative change in cross-sectional area of the tube is approximately thesame and of substantially the same order-at opposite ends of the end of which is axially spaced, as at I8, from the forward end of the tubular element I3, the

I pick-up tube I2 for introducing the foam forming solution into the water stream, the end 23 of the tube is so connected to the body of the foam I producer I8, as at 24*, that it is in free communication with the annular chamber I6. Consequently, as water under pressure is delivered to the device I8 and passes from the tubular member I3 to and through the sleeve I8 across the space I8, a suction is'induced in the region of said space sufficient to draw the stabilizer from its source of supply (not shown) through the pickup tube I2, into the chamber I6 and thence into the stream of water as it enters the sleeve I8. On

the'other hand, when the stabilizer pick-up tube is not employed, the pick-up tube opening in the wall of the main body ll of the foam producer is closed by a suitable plug, and in such case, the

water pre-mixed with the foam formingmaterial is delivered under pressure directly into the receiving end of the stream discharger or nozzlebutt I8.

In either case, the water laden with the foam forming material is discharged from the nozzle butt in the form of a turbulent stream for delivery into the interior of the foam discharge-tube .intermediate enlarged section 28, in consequence of which the foam stream is provided with a suddenly enlarged passage for its flow as it issues from the intake end section 21, this passage being as suddenly contracted as the foam enters the discharge end section 29 of the tube. As clearly appears in Figure 1, the said discharge end section 29 of the tube is relatively short in comparison with the length of the intermediate enlarged section 28. v

Fitted within the intermediate enlarged section 28 of the tube is a conical screen or baffle member 38, the apex of which is coaxial with the tube and points in the direction of the foam dischargeend thereof. Also, it may be desirable in certain instances to provide the interior ofthe section 28 of the tube with a stream straightener unit 3| consisting of a plurality of radially extending members 32, the inner edges of which are com-' monly secured together, as at 33, along a line coaxial with the tube and the outer edges of discharge tube 24 of the present invention is adapted to be employed in conjunction with any suitable stream discharge nozzle, such as is ex- 24, the latter being secured in any suitable manner in more or less closely spaced relation to the stream discharge end of the nozzle butt' I8. 'As

emplified by the nozzle I8 of Figures 1 and 2. In

the operation of the tube, the foam forming solution in finely subdivided and more or less highly turbulent state is directed at high velocity intothe intake section 21 of the tube, air being entrained with the liquid as it enters the tube to form the desired foam. The volume of foam so produced, expressed in gallons per minute, re-

mains, of course, relatively constant so long as the supply of water and foam forming material toand through the nozzle unit I8 remain unchanged, As the foam stream passes through '75 and issues from the intake section 21 of the tube auaooc .5 I at its initial high velocity, it retains its turbulent characterand if permitted to discharge from the tube in such state, the resultant stream would weep or spray in several directions. This is prevented, however, in the present case by reason of the fact that as the foam stream enters the enlarged section 28 of the tube and passes through the screen or baffle member III, its velocity is sharply reduced, approximately to one-half that of its initial velocity, in consequence of which the stream then partakes of a streamlined or laminar flow. Inasmuch as it is desired to maintain the volume of the foam (gallons per .minute flow thereof) constant as it passes through the tube, the cross-sectional area of the intermediate section of the tube is enlarged as described to compensate for the decrease in velocity of the foam stream which occurs as the latter encounters the resistance afforded by the screen or baffle member 30. It should be noted in this connection that the volume of the foam as measured in gallons per minute flow thereof is not increased as the foam enters the enlarged section 28 of the tube, the only change being in the velocity of the stream, which is so reduced within said section that the flow of the foam stream is converted from turbulent to streamlined character.

This change from turbulent to streamlined flow is effected within the length of the enlarged intermediate section 28 of the tube and while in such streamlined state, the foam stream is caused to pass into and through the discharge end section 29 of the tube, which is of such reduced crosssection as to increase the velocity of the stream to approximately its original value to thereby provide it with the desired range of projection from the tube; The discharge end section 29 of the tube is, however, of such limited length that the discharge therefrom of the high velocity, streamlined flow is effected without oportunity for the stream to revert to its original turbulent state. The result is that the foam stream issues from the discharge tube in the form of a solid,

pencil-like stream capable of being projected over a considerable distance for application of the foam to a localized area or spot.

Although it is not intended to limit the foam tube of the present invention to any particular dimensions or proportions of parts, by way of example it may be pointed out that it has been found generally preferable to form the intermediate section of the tube of a cross-sectional area approximately twice that of the cross-sectional area of the foam intake section 21, thereby reducing velocity of the stream for streamlining purposes to approximately one-half its initial value. The length of the section in which such streamlining is effected may, of course. vary depending upon variable factors, such as the volume of foam to be discharged by the tube, this length being ordinarily only such as is required for conversion of the flow from turbulent to streamlined condition.

It has been found, however, that in the larger capacity tubes such as are employed for the projection of relatively large volumes of foam, the enlarged intermediate section of the tube is required to be of some considerable length in order to afford suflicient time for the reduced velocity flow to convert from its original turbulent into its final streamlined character. This increase in length of the intermediate section of the tube is necessary, of course, because the increased volume of foam flowing through the larger capacity tubes is more diilicult to convert into a smooth-flowing the handling of the tube difflcult and to overcome this, the "stream-straightener" unit ll may well be employed.

This latter unit, as most clearly appears in Figure 4, sub-divides the cross-sectional area of the section 28 of the tube'in the region forwardly of the baflie member 30 into a plurality of passages each of which is traversed by a proportional amount of the total volume of ,foam discharged from the tube. The cross-sectional area of each such passages bears such relation to the length thereof that the volume of the foam passing therethrough under the reduced velocity may be andis streamlined within the length of the passage, each of the said passages 35 thus acting upon a limited portion of the total volume of the foam with the result that the foam stream in its entirety is completely streamlined prior to its discharge from the reduced end section 28 of the tube. Of course, the number of streamstraightening passages 35 may be varied as re-. quired to produce the desired result.

As illustrating the effectiveness of the streamstraightener for reducing the overall length of a foam tube of the larger capacity, a tube of a capacity to handle 1200 gallons of foam per minute was originally designed so that the eflective length of the enlarged intermediate section was approximately 24 inches between its discharge end and the apex of the conical baiile. Upon fitting a 9 inch long stream-straightener within this enlarged section of the tube and reducing the length of said section beyond the apex of the baflle to only twelve inches, the overall length of the tube was shortened by twelve inches, the foam stream discharged from such shortened tube being in all respects comparable with the solid, pencil-like stream of the longer tube not equipped with the stream-straightener.

While in its preferred construction, the enlarged intermediate section of the tube includes capable of being sufficiently reduced by the frictional resistance to the free flow thereof which is imparted solely by the internal surfaces of the said intermediate section. Also, in order to obtain the greatest possible expansion of the foam, it is desirable that the interposed resistance to the flow of the foam be of such order that while it suiliciently reduces the velocity of the foam stream for a streamlined flow thereof, it is insufficient to develop a back-pressure in the tube which would interfere with the maximum possible entrainment of air into the stream and travel thereof forwardly through the tube.

It will be understood, of course. that the present invention is susceptible of various changes and modifications which may be made from time to time without departing from the general principles or real spirit thereof, and it is accordingly intended to claim the same broadly. as well as specifically, as indicated by the appended claims.

What is claimed as new and useful is: 1. In an apparatus for producing fire-extinguishing foam, a tube for directionally discharg- 7 ing foam in the form of a streamlined, high-velocity stream, said tube being characterized in that it includes entrance and discharge sections of such approximately qual cross-sectional areas as to provide for the flow of foam therethrough at high velocity and an intermediate section-of greater length than and approximately twice the cross-sectional area of said entrance section to provide for the flow of foam therethrough at reduced velocity, and flow impeding means operative to maintain substantially uniform and constant the volumetric rate of flow of the foam through the tube, the said intermediate section being extended forwardly of the said flow impeding means a distance greater than the length of said discharge section whereby to insure conversion of the foam stream into one of streamlinedflow prior to entry of said stream into the reduced discharge section of the tube, and said discharge section being of shorter length than the intermediate section so as not to materially affect or disrupt the streamlined condition of the foam discharged therefrom.

2. Inan apparatus for producing fire-extinguishingfoam, a tube for receiving the foam and discharging the same in the form of a substantially solid stream, said tube having entrance and discharge sections through which the foam flows at high velocity andan intermediate section of greater length than and approximately twice the cross-sectional area of said entrance section to Y section for reducing the velocity and so produce a streamlined flow of the foam through said intermediate section, the major length of said intermediate section extending forwardly of said savanna 8 bai'iie, and means disposed within said intermediate section and in advance of said baii'ie means for subdividing the body of foam flowing at said reduced velocity through said intermediate section, said means being disposed with its forward end adjacent said discharge section to provide for mergence of the foam into a single stream prior to its discharge from the discharge section of the foam tube.

FISHER L. BOYD. LEWIS W. BOERNER.

REFERENCES CITED The following references are of record in the file of this patent:

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